Journal of Constructional Steel Research
F. Flores a,b; F. Charney c,⁎; D. Lopez-Garcia b,d
a Department of Civil Engineering, University of Cuenca, Ecuador
b Department of Structural and Geotechnical Engineering, Pontificia Universidad Catolica de Chile, Chile
c Department of Civil and Environmental Engineering, Virginia Tech, United States
d National Research Center for Integrated Natural Disaster Management CONICYT/FONDAP/15110017, Chile
This paper investigates the influence of the stiffness and strength of gravity columns on the collapse performance of buildings that utilize steel special moment frames as the main seismic lateral load resisting system. The research centers on the development of a simple lumped column approach, where all the gravity columns are combined into one elastic, continuous, and pinned-base element. Once this approach was validated, 2-, 4- and 8-story buildings that were originally analyzed without the influence of gravity columns in the ATC 76-1 project were reanalyzed including gravity columns. The FEMA P-695 methodology was used to assess the collapse performance. The effect of having a different number of gravity columns and different column sections was modeled by varying the moment of inertia of the lumped gravity column. The results show that the gravity columns have a profound influence on the collapse performance of buildings, especially for taller structures. Moreover, it was found that the correlation between the results of the nonlinear static analyses and the nonlinear dynamic analysis, based on collapse evaluation, provides insight into the choice of an optimal section for the lumped column. This means, in turn, that the designer can determine the number and the size of gravity columns that are required to significantly improve the building's collapse performance.